First, we've got population. The world today has 6.8 billion people. That's headed up to about nine billion. Now, if we do a really great job on new vaccines, health care, reproductive health services, we could lower that by, perhaps, 10 or 15 percent.
https://www.ted.com/talks/bill_gates_innovating_to_zero/transcript?language=en
I watched it again and he still can be interpreted either way. Lowering “that” could mean the overall CO2 or could mean the sentence subject of Population, which is the element he is talking about IMO.
i do agree whoever wrote it deliberately made it sound like that.